The present invention relates to a refrigeration system, and more particularly to an apparatus and method for purging non-condensable gases from a refrigeration system.
In a conventional refrigeration system, particularly in low pressure centrifugal compressor systems, the leakage of air, water vapor, and other contaminating foreign gases into the system is a recognized problem. Such gases reduce the efficiency of the system since they tend to elevate the total pressure in the condenser, and thus more power is required from the compressor per unit of refrigeration. Also, these foreign gases tend to cling to the condenser tubes thereby reducing the total condensing surface area.
To remove these foreign gases from the system, it is common practice to draw a mixture of the gaseous refrigerant and foreign gases from the high pressure region in the condenser or receiver where they normally accumulate, condense the refrigerant and any water vapor by cooling or by compression and cooling, vent off the non-condensables, separate and drain the water, and return the condensed refrigerant to the low pressure region of the system. Typically a purge apparatus is used to remove foreign gases from the refrigeration system in the above manner. A conventional purge apparatus typically comprises a purge chamber wherein the non-condensables gather above the liquid refrigerant and water. A pressure actuated mechanical relief valve automatically opens to vent the non-condensables to the atmosphere through a gas discharge line, and a manual drain is provided to drain off the water which floats on top of the liquid refrigerant. A mechanical valve adjacent the bottom of the purge chamber is opened by a float to drain the condensed refrigerant through a refrigerant line and return it to the low pressure region of the system.
While conventional purge apparatuses are efficient, it is recognized that non-condensed refrigerant remains with the contaminating non-condensable gases in the purge chamber and is vented to the atmosphere through the gas discharge line during the purging operation. Modern purge apparatuses include many refinements and, as a result, are more efficient than conventional purge apparatuses. However, it is recognized that even modern purge apparatuses vent some refrigerant to the atmosphere. Refrigerant that is vented to the atmosphere may adversely affect the environment. Also, each time refrigerant is vented to the atmosphere, the amount of refrigerant contained in the refrigeration system is decreased; therefore, after some period of time, refrigerant must be added to the refrigeration system to replace that which has been vented to the atmosphere.
There is a need, therefore, for a purge apparatus and method that substantially eliminates the venting of refrigerant to the atmosphere.